1. Field of the Invention
The present invention relates to a cup holder provided within the room of an automobile and, in more detail, relates to a cup holder having a holding claw capable of holding the side surface of a beverage container housed in a housing space.
2. Related Art
Cup holders each for stably holding a beverage container are provided within the room of an automobile. Many of the cup holders are provided with holding claws each for stably holding beverage containers of various sizes with respect to the acceleration and vibration of an automobile.
Such the cup holder is generally configured in a manner that the holding claw urged so as to protrude into the housing space is moved backward when the beverage container is housed within the housing space. The holding claw has the following mechanism, for example, that the holding claw has a swingable shaft at the upper portion thereof and holds a beverage container at the lower portion thereof (see Japanese Patent No. 3991045, for example), or the holding claw has a swingable shaft at the lower portion thereof and holds a beverage container at the upper portion thereof (see JP-A-2007-161086, for example), or the holding claw swings around a swingable shaft extending in the vertical direction (see JP-A-2006-224961, for example).
FIG. 10 is a sectional view explaining the structure of the cup holder described in JP-A-2007-161086. The cup holder 60 includes a cylindrical cup holder main body 62 which has a bottom portion and has a housing space 61 for housing a beverage container C, holding claws 64 each configured in a manner that the holding claw swings around a hinge portion 63 as a swingable shaft provided at the lower portion thereof and an abutment convex portion 64a provided at the upper portion of the holding claw moves respectively in the forward and backward directions to thereby move into and out of the housing space 61, and an annular rubber member 65 for urging the holding claws 64 in the direction where the holding claws 64 move forwardly.
The three holding claws 64 are provided with an equal interval so as to surround the beverage container C housed in the housing space 61 from the circumferential direction thereof (only one holding claw 64 is shown in the figure). When the beverage container C is housed in the housing space 61, since the abutment convex portions 64a are pushed by the side surface of the beverage container C, the holding claws 64 move backward to thereby hold the side surface of the beverage container C by the abutment convex portions 64a. 
Since the cup holder 60 has the swingable shaft at the lower portion of each of the holding claws 64, the beverage container C can be held at the higher position of the side surface of the beverage container C as compared with the cup holder having the swingable shaft at the higher portion of each of the holding claws. The beverage container C can be held more stably as the position for holding the beverage container becomes higher.
The cup holder having such the holding claws is required not only to have holding efficiency capable of stably holding various sizes of beverage containers but also to secure usability attained by suppressing a resistance force to the minimum at the time of inserting and taking out the beverage container. In order to satisfy both the holding efficiency and the usability, usually, a pressing force (for example, R60 in FIG. 10) for holding the side surface of the beverage container by the holding claws is set to be 1 to 5 N and the height (for example, Y60 in FIG. 10) for holding the beverage container by the holding claws is set to be 35 to 40 mm.
According to this cup holder 60, the beverage container C can be held stably with respect to the acceleration and the vibration of an automobile in a case of housing the beverage container C of a small diameter without inclining the holding claws 64 at an advanced reference position where the holding claws 64 are mostly advanced or moved forwardly into the housing space 61 and in a case of inclining the holding claw 64 at the maximum to house and support the beverage container C of a large diameter by the inner surface of the cup holder main body 62. However, there arises a problem in the holding efficiency in a case of the container of a middle diameter in a state that the holding claw 64 slightly moves backward from the advanced reference position. This problem will be explained concretely.
In FIG. 10, when an acceleration in the horizontal direction according to the acceleration and the vibration of an automobile acts on the beverage container C toward the right direction, since an inertial force F60 acts on the center of the gravity G60 of the container toward the horizontal and right direction, the beverage container C is forced to be fallen down. On the other hand, since the pressing force R60 acts on the side surface of the beverage container C in the horizontal and left direction from the portion 64a of the holding claw 64, the beverage container C is prevented from being fallen down. Supposing that a vertical distance to the center of the gravity G60 from the bottom surface of the beverage container C is X60 and a vertical distance the acting point of the pressing force R60 from the bottom surface of the beverage container C is Y60, the stability of the beverage container C is kept when a balance expression that an overturning moment (F60×X60) is smaller than a resisting moment (R60×Y60) is satisfied. The acceleration in the horizontal direction according to the acceleration and the vibration of an automobile sometimes becomes about 0.7 time (0.7 G) as large as the gravitational acceleration. In this case, the inertial force F60 becomes same as 0.7×W60 (W60: the weight of the beverage container C). Although the restoring moment due to the weight W60 of the beverage container C acts to reduce the overturning moment, the restoring moment will not be taken into consideration in this case as an element for considering the dangerous side.
In the case of supposing a can of 250 ml of the standard size as the beverage container C of the small diameter, the weight W60 of the beverage container is 2.7 N and the vertical distance X60 is 66.5 mm. Further, in the case of supposing a condition for setting the holding efficiency of the holding claw 64 to the highest level within the related art condition, the pressing force R60 is 5 N and the vertical distance Y60 is 40 mm. According to these conditions, the overturning moment will be F60×X60=0.7×2.7 N×66.5 mm=125.69 N·mm, and the resisting moment will be R60×Y60=5 N×40 mm=200 N·mm. Thus, since the overturning moment is smaller than the resisting moment, the stability of the beverage container C can be kept sufficiently.
In contrast, in the case of supposing a plastic bottle of 500 ml of the standard size as the beverage container C of the middle diameter, the weight W60 of the beverage container is 5 N and the vertical distance X60 is 92.5 mm. Further, as described above, in the case of supposing the condition for setting the holding efficiency of the holding claw 64 to the highest level, the overturning moment will be F60×X60=0.7×5 N×92.5 mm=323.75 N·mm, and the resisting moment will be R60×Y60=5 N×40 mm=200 N·mm. Thus, since the overturning moment is larger than the resisting moment, the stability of the beverage container C can not be kept.
In this manner, according to the cup holder 60 of the related art, even if the condition for setting the holding efficiency to the highest level within the related art condition is taken into consideration, there arises a problem that the beverage container C of the middle diameter can not be held stably with respect to the acceleration of 0.7 G in the horizontal direction according to the acceleration and the vibration of an automobile.
Further, when the pressing force R60 of the holding claw 64 is increased in order to improve the holding efficiency of the cup holder 60, since the resistance force at the time of inserting and taking out the beverage container C increases, good usability cannot be obtained. This problem is not peculiar to the cup holder 60 of described in the patent document 2 but common to Japanese Patent No. 3991045, JP-A-2007-161086 and JP-A-2006-224961.
Further, in the cup holder which is configured in a manner that the holding claw has the swingable shaft at the upper portion thereof and holds the beverage container at the lower portion thereof like Japanese Patent No. 3991045, when the pressing force of the holding claw is increased, the force of the holding claw for raising up the beverage container increases. Thus, when the weight of the beverage container is small due to the small amount of remaining beverage within the beverage container, the beverage container may be popped up from the cup holder. In this manner, the cup holder having the holding claws according to the related art can not sufficiently satisfy both the holding efficiency and the usability.